1. Field of the Invention
The invention relates to passive radio frequency identification (RFID) chips, and more particularly, to a passive RFID chip with a protection function against high-intensity electromagnetic fields.
2. Description of Related Art
FIG. 1 shows a schematic circuit diagram of a typical passive RFID chip in the existing arts. The passive RFID chip 1 includes an antenna 100, a power unit 200 connected to the antenna 100, an input/output circuit 300, and a logic circuit 400 both connected to the power unit 200. The typical passive RFID chip 1 receives electromagnetic waves 8 from an RFID reader and operates according to electromagnetic energy carried by the electromagnetic waves.
The antenna 100 receives the electromagnetic waves 8 from the RFID reader and generates AC (alternating current) electrical signals to output to the power unit 200. The power unit 200 includes two diodes and two capacitors that are connected in a form for rectifying and smoothing the electrical signals sent by the antenna 100 and outputting a stable DC (direct current) voltage VDD. In this sense, the power unit 200 serves as a DC voltage source and supplies power to the input/output circuit 300 and the logic circuit 400.
The significant advantage of the typical passive RFID chip is that the typical passive RFID chip enables an RFID reader to retrieve identifying information from an RFID device that is configured with the typical passive RFID chip wirelessly. The RFID device only needs to be positioned near the RFID reader to easily retrieve the identifying information. However retrieving the identifying information at a relative longer distance is also desired. But, to retrieve identifying information at a longer distance, the RFID reader needs to generate high-energy electromagnetic waves. Accordingly, the DC voltage VDD outputted by the power unit 200 would also increase, and may damage the logic circuit 400 of the typical RFID chip.
Therefore, a heretofore unaddressed need exists in the industry to overcome the aforementioned deficiencies and inadequacies.